"use strict";

/**
 * @desc   base64加解密
 */
var base64 = {
  // private property
  _keyStr: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",
  // public method for encoding
  encode: function encode(input, binary) {
    binary = binary != null ? binary : false;
    var output = "";
    var chr1, chr2, chr3, enc1, enc2, enc3, enc4;
    var i = 0;

    if (!binary) {
      input = base64._utf8_encode(input);
    }

    while (i < input.length) {
      chr1 = input.charCodeAt(i++);
      chr2 = input.charCodeAt(i++);
      chr3 = input.charCodeAt(i++);
      enc1 = chr1 >> 2;
      enc2 = (chr1 & 3) << 4 | chr2 >> 4;
      enc3 = (chr2 & 15) << 2 | chr3 >> 6;
      enc4 = chr3 & 63;

      if (isNaN(chr2)) {
        enc3 = enc4 = 64;
      } else if (isNaN(chr3)) {
        enc4 = 64;
      }

      output = output + this._keyStr.charAt(enc1) + this._keyStr.charAt(enc2) + this._keyStr.charAt(enc3) + this._keyStr.charAt(enc4);
    }

    return output;
  },
  // public method for decoding
  decode: function decode(input, binary) {
    binary = binary != null ? binary : false;
    var output = "";
    var chr1, chr2, chr3;
    var enc1, enc2, enc3, enc4;
    var i = 0;
    input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");

    while (i < input.length) {
      enc1 = this._keyStr.indexOf(input.charAt(i++));
      enc2 = this._keyStr.indexOf(input.charAt(i++));
      enc3 = this._keyStr.indexOf(input.charAt(i++));
      enc4 = this._keyStr.indexOf(input.charAt(i++));
      chr1 = enc1 << 2 | enc2 >> 4;
      chr2 = (enc2 & 15) << 4 | enc3 >> 2;
      chr3 = (enc3 & 3) << 6 | enc4;
      output = output + String.fromCharCode(chr1);

      if (enc3 != 64) {
        output = output + String.fromCharCode(chr2);
      }

      if (enc4 != 64) {
        output = output + String.fromCharCode(chr3);
      }
    }

    if (!binary) {
      output = base64._utf8_decode(output);
    }

    return output;
  },
  // private method for UTF-8 encoding
  _utf8_encode: function _utf8_encode(string) {
    string = string.replace(/\r\n/g, "\n");
    var utftext = "";

    for (var n = 0; n < string.length; n++) {
      var c = string.charCodeAt(n);

      if (c < 128) {
        utftext += String.fromCharCode(c);
      } else if (c > 127 && c < 2048) {
        utftext += String.fromCharCode(c >> 6 | 192);
        utftext += String.fromCharCode(c & 63 | 128);
      } else {
        utftext += String.fromCharCode(c >> 12 | 224);
        utftext += String.fromCharCode(c >> 6 & 63 | 128);
        utftext += String.fromCharCode(c & 63 | 128);
      }
    }

    return utftext;
  },
  // private method for UTF-8 decoding
  _utf8_decode: function _utf8_decode(utftext) {
    var string = "";
    var i = 0;
    var c = c1 = c2 = 0;

    while (i < utftext.length) {
      c = utftext.charCodeAt(i);

      if (c < 128) {
        string += String.fromCharCode(c);
        i++;
      } else if (c > 191 && c < 224) {
        c2 = utftext.charCodeAt(i + 1);
        string += String.fromCharCode((c & 31) << 6 | c2 & 63);
        i += 2;
      } else {
        c2 = utftext.charCodeAt(i + 1);
        c3 = utftext.charCodeAt(i + 2);
        string += String.fromCharCode((c & 15) << 12 | (c2 & 63) << 6 | c3 & 63);
        i += 3;
      }
    }

    return string;
  }
};
module.exports = base64;